1. Field of the Invention
The present invention concerns methods for decreasing the frequency of transmission of viral infection, such as human immunodeficiency virus and herpesvirus, by administration of cellulose acetate phthalate or hydroxypropyl methylcellulose phthalate, which were heretofore employed as pharmaceutical excipients.
2. Background Information
Pharmaceutical excipients are defined as inert substances that form a vehicle for drug delivery (Webster's Ninth New Collegiate Dictionary, Merriam-Webster Inc. Publishers, Springfield, Mass., USA, 1985, p. 432). Thus, excipients convert pharmacologically active compounds into pharmaceutical dosage forms suitable for administration to patients. Some excipients are also used for the formulation or production of confectionery, cosmetics and food products. Therefore, approved excipients are used frequently and at higher dosage levels in comparison with most drugs. Excipients are also much less expensive and more easily produced in very large scale in comparison with most drugs.
Human immunodeficiency viruses ("HIV") have been known as the causative virus for AIDS (Acquired Immunodeficiency Syndrome). The prevalence of AIDS cases is presently increasing at an alarming rate.
Two related retroviruses that can cause AIDS are human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2). The genomes of these two viruses are about 50% homologous at the nucleotide level, contain the same complement of genes, and appear to attack and kill the same human cells by the same mechanism.
HIV-1 was identified in 1983. Virtually all AIDS cases in the United States are associated with HIV-1 infection. HIV-2 was isolated in 1986 from West African AIDS patients.
HIV-1 and HIV-2 are retroviruses in which the genetic material is RNA, rather than DNA. The HIV-1 and HIV-2 viruses carry with them a polymerase (reverse transcriptase) that catalyzes transcription of viral RNA into double-helical DNA.
The viral DNA can exist as an unintegrated form in the infected cell or be integrated into the genome of the host cell. As presently understood, the HIV enters the T4 lymphocyte where it loses its outer envelope, releasing viral RNA and reverse transcriptase.
The reverse transcriptase catalyzes synthesis of a complementary DNA strand from the viral RNA template. The DNA helix then inserts into the host genome where it is known as the provirus. The integrated DNA may persist as a latent infection characterized by little or no production of virus or helper/inducer cell death for an indefinite period of time. When the viral DNA is transcribed and translated by the infected lymphocyte, new viral RNA and proteins are produced to form new viruses that bud from the cell membrane and infect other cells.
Attempts to treat AIDS with drugs which inhibit reverse transcriptase such as 3'-azido-3'-deoxythymidine (AZT) have not been met with a desirable degree of success. Moreover, there is a potential for toxicity with the use of anti-viral drugs. Thus there is a need for an effective and safe means to prevent and treat AIDS.
HIV infections are transmitted by means such as contaminated intravenous drug needles and through sexual contact. Sexual transmission is the most frequent (86%) route of adult HIV-1 infections worldwide (AIDS in the World, Harvard University Press, Cambridge, Mass., (1992)).
The transmission of HIV by heterosexual sex poses an especially severe problem for women. By the year 2,000, it is estimated that 90% of HIV infections will be acquired via heterosexual intercourse.
The utilization of condoms provides a substantial degree of protection against transmission of HIV and herpesvirus infections during sexual intercourse, but a difficulty arises when condoms are not employed. Moreover, the use of condoms appears to be a culturally and socially unacceptable practice in many countries.
Although men can protect themselves from sexually transmitted HIV and herpesvirus infection by using condoms, women who are sexually active have no similar means. Women can encourage their male sex partners to use a condom, but may not succeed. The female condom, which is just becoming available, is expensive and there is presently no evidence that it prevents sexual transmission of HIV or herpesvirus.
Even maintaining a monogamous sexual relationship is no guarantee of safety, for if a woman's male partner becomes infected, he can pass the virus to her. And as more women are infected, so are more babies.
There is presently frustration in the medical field by the bleak prospect for an effective AIDS vaccine in the near future and the severe limitations of drugs that effectively and safely combat HIV.
Due to the present absence of a prophylactic anti-HIV vaccine and because of limitations of educational programs, other preventive methods have been sought. Spermicides with virucidal properties have been considered for this purpose, but their application is contraindicated by adverse effects (Bird, K. D., "The Use of Spermicide Containing Nonoxynol-9 in the Prevention of HIV Infection", AIDS, 5, 791-796 (1991)).
Anti-HIV drugs currently in use or expected to be clinically applied in the near future (Steele, F., "AIDS Drugs Lurch Towards Market", Nature Medicine, 1, 285-286 (1995)) are mostly not targeted to the earliest steps in the virus replicative cycle, lead to the emergence of drug resistant mutants, and are expensive, suggesting that their application for wide use in topical chemoprophylaxis is unlikely.
Cells which are the primary targets for sexual and mucosal transmission of HIV, either in the form of free virus or virus-infected cells, have not been fully defined and may be diverse (Miller, C. J. et al., "Genital Mucosal Transmission of Simian Immunodeficiency Virus: Animal Model for Heterosexual Transmission of Human Immunodeficiency Virus", J. Virol., 63, 4277-4284 (1989); Phillips, D. M. and Bourinbaiar, A. S., "Mechanism of HIV Spread from Lymphocytes to Epithelia", Virology, 186, 261-273 (1992); Phillips, D. M., Tan, X., Pearce-Pratt, R. and Zacharopoulos, V. R., "An Assay for HIV Infection of Cultured Human Cervix-derived Cells", J. Virol. Methods, 52, 1-13 (1995); Ho, J. L. et al., "Neutrophils from Human Immunodeficiency Virus (HIV)-SeronegatiVe Donors Induce HIV Replication from HIV-infected Patients Mononuclear Cells and Cell lines": An In Vitro Model of HIV Transmission Facilitated by Chlamydia Trachomatis., "J. Exp. Med., 181, 1493-1505 (1995); and Braathen, L. R. & Mork, C. in "HIV infection of Skin Langerhans Cells", In: Skin Langerhans (dendritic) cells in virus infections and AIDS (ed. Becker, Y.) 131-139 (Kluwer Academic Publishers, Boston, (1991)). Such cells include T lymphocytes, monocytes/macrophages and dendritic cells, suggesting that CD4 cell receptors are engaged in the process of virus transmission (Parr, M. B. and Parr, E. L., "Langerhans Cells and T lymphocyte Subsets in the Murine Vagina and Cervix", Biology of Reproduction, 44, 491-498 (1991); Pope, M. et al., "Conjugates of Dendritic Cells and Memory T Lymphocytes from Skin Facilitate Productive Infection With HIV-1", Cell, 78, 389-398 (1994); and Wira, C. R. and Rossoll, R. M., "Antigen-presenting Cells in the Female Reproductive Tract: Influence of Sex Hormones on Antigen Presentation in the Vagina", Immunology, 84, 505-508 (1995)).
Therefore agents blocking HIV-CD4 binding are expected to diminish or prevent virus transmission. Soluble recombinant CD4 cannot be considered for this purpose since high concentrations are required to neutralize the infectivity of primary HIV isolates (Daar, E. S., Li, X. L., Moudgil, T. and Ho, D. D., "High Concentrations of Recombinant Soluble CD4 are Required to Neutralize Primary Human Immunodeficiency Virus Type 1 Isolates", Proc. Natl. Acad. Sci. U.S.A., 87, 6574-6578 (1990), and in the case of SIV, the infectivity is enhanced by CD4 (Werner, A., Winskowsky, G. and Kurth, R., "Soluble CD4 Enhances Simian Immunodeficiency Virus SIVagm Infection", J. Virol., 64, 6252-6256 (1990)). However, anti-CD4 antibodies are expected to prevent virus transmission independently of subtype and variability, but their application would be too costly (Daar et al, supra, Watanabe, M., Boyson, J. E., Lord, C. I. and Letvin, N. L. "Chimpanzees Immunized with Recombinant Soluble CD4 Develop Anti-self CD4 Antibody Responses with Anti-human Immunodeficiency Virus Activity", Proc. Natl. Acad. Sci. U.S.A., 89, 5103-5107 (1992); and Perno, C. -F., Baseler, M. W., Broder, S. and Yarchoan, R., "Infection of Monocytes by Human Immunodeficiency Virus Type 1 Blocked by Inhibitors of CD4-gp120 Binding, Even in the Presence of Enhancing Antibodies", J. Exp. Med., 171, 1043-1056 (1990)).
There is a need for a safe and effective substance that can be inserted into the vagina by a foam, gel, sponge or other form to prevent HIV-1 or HIV-2 from infecting cells in the body. It is hoped that such substance be used by a woman without her partner's knowledge.
Prospects for the near and possibly not so near future to prevent HIV-1 transmission by vaccination do not seem good. A recent report that vaccination with inactivated SIV did not protect African Green monkeys against infection with the homologous virus notwithstanding a strong immune response to SIV does not appear to be encouraging in this respect (Siegel, F., Kurth, R., and Norley, S., (1995), "Neither Whole Inactivated Virus Immunogen nor Passive Immunoglobulin Transfer Protects Against SIV.sub.agm Infection in the African Green Monkey Natural Host", J. AIDS, 8, 217-226). Considering this problem, emphasis has been put on attempts to build a chemical barrier to HIV-1 transmission (Taylor, (1994), "Building a Chemical Barrier to HIV-1 Transmission", J. NIH Res., 6, 26-27).
The development of topically applied microbicides, expected to prevent sexual (mucosal) transmission of HIV-1, was suggested to need to be "effective against all sexually transmitted diseases and should not be seen, smelled, or felt while in use." It should also be inexpensive and widely available, and $25 million was expected to be devoted to its development in the United States in 1995 (Taylor,(1994) supra). Detergents (nonoxynol-9) as a universal pathogen killer have been selected for clinical trials. However, not surprisingly, this compound proved to be deleterious to the host.
Targeting the chemical barrier to transmission of individual pathogens could perhaps facilitate the development of compounds preventing the transmission of human immunodeficiency viruses. For example, effective blockade of receptors for the viruses might accomplish this goal. This concept may be supported by the finding that immunization of chimpanzees and rhesus monkeys, respectively, with human CD4 which has several amino acid point mutations in comparison with non-human primate CD4 sequences (Fomsgaard, A., Hirsch, V. M., and Johnson, P. R., (1992), "Cloning and Sequences of Primate CD4 molecules: Diversity of the Cellular Receptor for Simian Immunodeficiency Virus/Human Immunodeficiency Virus", Eur. J. Immunol., 22, 2973-2981), developed anti-CD4 antibodies which inhibited HIV-1 and SIV replication (Watanabe, M., Levine, C. G., Shen, L., Fisher, R. A., and Letvin, N. L. (1991), "Immunization of Simian Immunodeficiency Virus-Infected Rhesus Monkeys with Soluble Human CD4 Elicits an Antiviral Response," Proc. Natl. Acad. Sci. USA, 88, 4616-4620. Watanabe, M., Chen, Z. W., Tsubota, H., Lord, C. I., Levine, C. G., and Letvin, N. L., (1991), "Soluble Human CD4 Elicits an Antibody Response in Rhesus-Monkeys that Inhibits Simian Immunodeficiency Virus Replication", Proc. Natl. Acad. Sci. USA, 88, 120-124; and Watanabe, M., Boyson, J. E., Lord, C. I., and Letvin, N. L., (1992), "Chimpanzees Immunized with Recombinant Soluble CD4 Develop Anti-self CD4 Antibody Responses with Anti-human Immunodeficiency Virus Activity", Proc. Natl. Acad. Sci. USA, 89, 5103-5107).
Herpesviruses include the following viruses isolated from humans:
(1) herpes simplex virus 1 ("HSV-1") PA1 (2) herpes simplex virus 2 ("HSV-2") PA1 (3) human cytomegalovirus ("HCMV") PA1 (4) varicella-zoster virus ("VZV") PA1 (5) Epstein-Barr virus ("EBV") PA1 (6) human herpesvirus 6 ("HHV6") PA1 (7) herpes simplex virus 7 ("HSV-7") PA1 (8) herpes simplex virus 8 ("HSV-8")
Herpesviruses have also been isolated from horses, cattle, pigs (pseudorabies virus ("PSV") and porcine cytomegalovirus), chickens (infectious larygotracheitis), chimpanzees, birds (Marck's disease herpesvirus 1 and 2), turkeys and fish (see "Herpesviridae: A Brief Introduction", Virology, Second Edition, edited by B. N. Fields, Chapter 64, 1787 (1990)).
Herpes simplex viral ("HSV") infection is generally a recurrent viral infection characterized by the appearance on the skin or mucous membranes of single or multiple clusters of small vesicles, filled with clear fluid, on slightly raised inflammatory bases.
The herpes simplex virus is a relatively large-sized virus. HSV-2 commonly causes herpes labialis. HSV-2 is usually, though not always, recoverable from genital lesions. Ordinarily, HSV-2 is transmitted venereally.
The time of initial herpes simplex virus infection is usually obscure except in the uncommon primary systemic infection occurring in infants and is characterized by generalized cutaneous and mucous membrane lesions accompanied by severe constitutional symptoms. Localized infections ordinarily appear in childhood, but may be delayed until adult life. It is presumed that the herpes simplex virus remains dormant in the skin and that herpetic eruptions are precipitated by overexposure to sunlight, febrile illnesses, or physical or emotional stress; also, certain foods and drugs have been implicated. In many instances, the trigger mechanism remains undetected.
The lesions caused by herpes simplex virus may appear anywhere on the skin or on mucous membranes, but are most frequent on the face, especially around the mouth or on the lips, conjunctiva and cornea, or the genitals. The appearance of small tense vesicles on an erythematous base follows a short prodromal period of tingling discomfort or itching. Single clusters may vary from 0.5 to 1.5 cm in size, but several groups may coalesce. Herpes simplex on skin tensely attached to underlying structures (for example, the nose, ears or fingers) may be painful. The vesicles may persist for a few days, then begin to dry, forming a thin yellowish crust. Healing usually occurs within 10 days after onset. In moist body areas, healing may be slower, with secondary inflammation. Healing of individual herpetic lesions is usually complete, but recurrent lesions at the same site may result in atrophy and scarring.
In females infected with HSV-2, there may be no skin lesions, the infection may remain entirely within the vagina. The cervix is frequently involved, and there is increasing evidence that this may be a factor in the development of carcinoma of the cervix.
Corneal lesions commonly consist of a recurrent herpetic keratitis, manifest by an irregular dendritic ulcer on the superficial layers. Scarring and subsequent impairment of vision may follow.
Gingivostomatitis and vulvovaginitis may occur as a result of herpes infection in infants or young children. Symptoms include irritability, anorexia, fever, inflammation, and whitish plaques and ulcers of the mouth. Particularly in infants, though sometimes in older children, primary infections may cause extensive organ involvement and fatal viremia.
In women who have an attack of HSV-2 late in pregnancy, the infection may be transmitted to the fetus, with the development of severe viremia. Herpes simplex virus may also produce fatal encephalitis.
Kaposi's varicelliform eruption (eczema herpeticum) is a potentially fatal complication of infantile or adult atopic eczema. Exposure of patients with extensive atopic dermatitis to persons with active herpes simplex should be avoided.
No local or systemic chemotherapeutic agent has been demonstrated to be effective for treating herpes simplex virus with the possible exception of topical idoxuridine (IDU) in superficial herpetic keratitis. Reports on this compound in cutaneous herpes are conflicting. Other drugs which have been employed to treat HSV include trifluorothymidine, vidarabine (adenine arabinoside, ara-A), acyclovir, and other inhibitors of viral DNA synthesis may be effective in herpetic keratitis. These drugs inhibit herpes simplex virus replication and may suppress clinical manifestations. However, the herpes simplex virus remains latent in the sensory ganglia, and the rate of relapse is similar in drug-treated and untreated individuals. Moreover, some drug-resistant herpes virus strains have emerged.
Diseases caused by varicella-zoster virus (human herpesvirus 3) include varicella (chickenpox) and zoster (shingles).
Cytomegalovirus (human herpesvirus 5) is responsible for cytomegalic inclusion disease in infants. There is presently no specific treatment for treating patients infected with cytomegalovirus.
Epstein-Barr virus (human herpesvirus 4) is the causative agent of infectious mononucleosis and has been associated with Burkitt's lymphoma and nasopharyngeal carcinoma.
Animal herpesviruses which may pose a problem for humans include B virus (herpesvirus of Old World Monkeys) and Marmoset herpesvirus (herpesvirus of New World Monkeys).
In searching for inexpensive antiviral compounds which could be applied topically to decrease the frequency of sexual transmission of the human immunodeficiency virus type 1 (HIV-1) and herpesviruses (HSV), applicants decided against all odds to screen excipients for anti-HIV-1 activity and discovered the present invention which involves the administration of cellulose acetate phthalate ("CAP") or hydroxypropyl methylcellulose phthalate ("HPMCP").